Railway traffic controlling apparatus



Nov.'4,l94l. H. NICHOLSON- v RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed March 30, 1938 5 p w m M w. 3 T ,....N W S k 0 v v mm m WW F n 2 w I I M 44 4 M? H 1 w p m m 7 6.VA w 1 m H 9. 5 l 6 Patented Nov. 4, 1941 Frank H. Nicholson, Wilkinsburg,-Pa.,assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Original application March 30; 1938', Serial No; 198,935. Divided and thisapplication February 3, 1940, Serial No. 317,157

germ-34) 11 Claims.

My invention relates to railway trafiic controlling apparatus and it has special reference to the organization of such apparatus into sys-' tems wherein various circuits are controlled inaccordance with the presence or absence of repeatedly recurring pulses of coded energy.

This application is a division of an-earlier case hearing Serial No. 198,935 which'was filed March 30, 1938 for Railway traflic' controlling apparatus and which matured into Patent No. 2,229,254 dated Jan. 21, 1941, and assigned to The Union Switch and Signal Company.

As in that earlier case, the broad object of the present invention isto facilitate various control functions which are peculiar to railway signaling.

A more specific object is to increasethe shunting sensitivity of continuously coded track cir-' cults.

Another object is to utilize the rails of a track section as dual-purpose conductors in a combined track and switch-detector circuit.

An additional object is to provide for the control and indication of the operation of arailway switch through the medium of but two line conductors between the switch and its control lever.

In practicing my invention I attain the above and other objects and advantages by usin'g'anenergy-storage device, such as'a capacitor, as a secondary source of power for a relay which is arranged to register an operating effect of a coding or other periodically movable contact. Under the control of this contact the secondary storage device is repeatedly connected first to a charging source and then to a discharging circuit which includes the winding of the operation-registering relay. That relay releases with sufiicient slowness as to bridge the periods between the successive energizing pulses which result and thus it responds to the presence or absence of the desired operating effect of the periodically movable contact referred to above.

I shall describe three-forms of railway trafilc controlling apparatus embodying my invention and shall then point out the novel features there-. of in claims. These embodim'entsare disclosed by the accompanying drawingv in which:

Figs. 1 and 2 show applications of my im-' 3 proved code-registering means to track circuits for'the purpose of improving their shunting sensitivity;

Fig. 3 shows the apparatus of the preceding figures applied to operate conjunction with air 55 awayside signal S combined track circuita-nd' switch-detector cir-' cuit; and

Fig. 4 is a showing of my improved equipment organized into a system for controlling and indidating the operation of a' railway switch over asingle pair- 'of line-circuit conductors.

' In the several-views of the drawing, likeref erence characters-designate corresponding parts. Referring first to Fig. 1, character X designates a; contact which is' adapted to move back and. forth between two positions and character KQ designates a'relay for responding to this backand-forth contact movement when such is regularly repeated. Each' time that contact X -occu-- piesits picked-up position (shown heavy) it completes a circuit'through which a direct-current source; shown in the form of a battery Q,

supplies charging current to anenergy-storagedevice; shown in the form of a capacitor K; Similarly, each time that-the contact X occupies its released position (shown dotted) it completes a circuit through which the capacitor K dissipates its stored energy by circulating" discharging current'through the winding of relay KQ.-

This relay KQ is provided with a contact 6 which is picked up in response to each pulse of capacitor discharge current and-which-is sumciently slow in' releasing as to bridge the in-' te'rvals'between consecutive pulses when contact- X is repeatedly shifted at normal code-pulse ratebetween the two positions just described-.-

In practice it is found that a capacitor of comparatively large energy-storage capacity is need-- ed to effect the'described operation of relay KQ under code-following conditions on the part of contact X, and for this reason a device of the electrolytic type will in many instances be-found preferable because of its comparatively smaller physical dimensions for a given energy-storage rating.

In the'particular application of" my improved (code registering which is represented in Fig. l,

the rails I and 2 of a track sectionIJ are employed as conductors in the charging and discharging circuit for the energy-storage. device-K.

As already pointed out, the capacitor-chargingcurrent originates in battery Q and the discharging' current is normally passed through a circuit whichincludes the winding of slow release relay KQ. The up-and-down moving contact- X forms a part of a constantly operating coding device CT and contact 6 of relay KQ is shown-1 as selectively controlling' the lamps G and R ofwhich' is positioned the entranceof the associated track section in the usual manner.

As long as this track section IJ remains vacant, contact X repeatedly connects the capacitor K first with the battery Q and then with the winding of relay KQ. The charging circuit may be traced from the positive terminal of source Q through conductor I, front contact X of device CT, conductor 8, track rail 2, conductor 2|, the capacitor K, conductor 22, track rail I and conductor IO back to the negative terminal of source Q. The referred to discharging circuit extends from the left or positively charged plate of capacitor K through conductor 2|, track rail 2, conductor 8, back contact X of device CT, conductor II the winding of relay KQ, conductor Ill, track rail I and conductor 22 back to the right or negatively charged plate of the capacitor.

Under the stated condition of track section vacancy, relay KQ thus receives recurring pulses of energizing current which maintain its contact 6 continuously picked up. In consequence, lamp G of wayside signal Si now receives lighting current over a circuit which may be traced from the positive terminal of a suitable supply source through front contact 6 of relay KQ, conductor 23 and the lamp G. back to the negative terminal of the supply source. The resulting aspect of a green light indicates that the entire length of the track section IJ is clear.

In the event, now, that a train enters the track section IJ, the shunting action of its wheels and axles provides a by-pass or short circuit of both the charging and the discharging circuits for the capacitor K. This, of course, produces a continuous deenergization on the part of relay KQ which causes it to drop its contact B to the released position. Under this condition, the controlled wayside signal Si displays the red or stop" indication as a result of lamp R receiving lighting current over a circuit which extends from the positive supply terminal through back contact 6 of relay KQ, conductor 24 and the lamp R back to the negative supply terminal.

As soon as the track section is again vacated, the accompanying removal of the shunting path between the track rails I and 2 allows pulses of charging current again to be transmitted to the capacitor K and pulses of discharging current to be transmitted from this capacitor to the Winding of relay KQ. In responding in the manner already explained, this relay causes the controlled wayside signal S again to display the green or clear indication. 7

By employing the arrangement of Fig. 1, I have discovered that the sensitivity of trackcircuit shunting may be substantially increased. This is because of the fact that whenever a shunt is placed across the rails I and 2 not only is the energy which battery Q supplies to the capacitor K by-passed but also the discharge current from this capacitor is also circulated through the shunting path. This means that at the moment of initial shunting, energy from both directions is available for breaking down the high resistance film between the running surfaces of the rails I and 2 and the contacting surfaces of the train wheels. By virtue of this dual-direction supply the action just referred to is made more positive and rapid and in this manner the shunting sensitivity of the track circuit is substantially increased.

A capacitor of the type shown at K in Fig. 1

is not the only energy-storage device which may be employed for the purpose stated. If desired, use may also be made of a direct-current shuntwound motor arranged as shown at KM in Fig. 2. When supplied through rails I and 2 with the recurring pulses of energizing current from direct-current source Q at location I (not shown in Fig. 2) such a motor may be designed to rotate at a substantial rate of speed. Preferably, the armature or rotating member thereof should be arranged, as by the use of a fly wheel, to have a relatively high value of rotative inertia in order that the speed may be sustained during the 01f periods of motor supply current.

On the occasion of each of these periods, this stored rotative energy causes the machine KM to operate as a generator and supply current in the opposite direction through the rails I and 2 back to the winding of relay KQ at location I. Thus it will be seen that the motor-energizing circuit is identical with the capacitor-charging circuit represented in Fig. 1 and that the-circuit through which current generated by machine KM passes during intervening periods is identical with thedischarging circuit for the capacitor KofFig'l.

The modified arrangement of Fig. 2 is, therefore, effective to increase the sensitivity of trackcircuit shunting in the same manner as does the arrangement of Fig. 1. That is, when the train wheels and axles first by-pass the rails I and 2 of track section IJ, the machine KM at the exit end of the section supplies generated current to the point of wheel contact which aids the current from battery Q in breaking down the initial resistance between the running surfaces of the rails and the contacting surfaces of the train wheels.

Referring to Fig. 3, a second application of the improvements of my invention is there shown in connection with a combined track circuit and switch-detector circuit. The track circuit includes the rails I and 2 between locations U and .V and the track switch is associated with 1. the-rails ofa branch line track 4I42.

Again use is made of the energy-storage device K bridged across the rails I and 2 of the track section, a source of charging current Q periodically connected to the rails by contact X of a constantly operating coding device CT and a slow release relay KQ arranged to receive discharging current from capacitor K over contact X when in the released position. In addition, use also is made of contacts 43 and M of the usual switch circuit controller for the purpose of interrupting the connection of the capacitor K with the track rails each time that the points of the switch are shifted from the normal position in which traffic moving in the direction of the arrow continues along the main line rails I and 2 to the reversed position in which the trafiic is diverted to the branch track rails II-42.

The slow-release relay KQ serves the dual purpose of indicating whether the track section UV is occupied and also of whether the points of the referred to track switch occupy the reversed or traffic-diverting position. As long as neither of these conditions obtains, the contact 6 of relay KQ occupies the picked-up position shown. When, however, either of the two stated conditions-becomes effective, the relay contact is dropped to its released position.

The above comes about in the following manner. With the track section vacant and the track switch inthe normal position, each pickup operation on the part of the constantly operating contact X of device CT. completes for .energy-storage device K a charging circuit which may be traced from the positive supply terminal of battery Q, through conductorl, front contact X of device CT, conductor 8, the track rail 2, conductor 2|", switch-controller contact 44, the capacitor K, switch-controller contact 43,- conductor 22, track rail I and conductors l0 and I6 back to the negative terminal of battery Q. Likewise, each releasing operation of coding contact X completes a' circuit through which capacitor K circulates its discharge current through the winding of relay KQ. This circuit may be traced from the lower or positively charged plate of storage device K through switch-controllercontact 44, conductor 2|, track railZ, conductor 3, back contact X of device CT, conductor II, the winding of relay KQ, conductor I0, track rail I, conductor 22 and switch-controller contact 33 back to the upper or negatively charged plate of the capacitor.

Under the stated conditions of vacant track section and normal switch position, relay KQ thus receives repeated pulses of energizing current which cause this slow-releasing device to maintain its contact 6 continuously picked up.

In the event, now, that a train comes into the section UV, the shunting action of its j wheels and axles icy-passes the rails l and 2 and thus discontinues the supply of energizing pulses to relay KQ. In consequence, it drops its contact 6 to the released position. Likewise, with the track section U--V vacant, when the points of the switch associated with the branchtrack rails 4| and 42 are shifted to the traflicdiverting position, switch-controller contacts 43 and M disconnect the capacitor K from the rails I and 2 and thus also discontinue the supply of energizing pulses to the relay KQ. Under this second condition, therefore, that relay also releases, its contact. 7

Referring finallyto Fig. 4, the improved coderegistering apparatus of my invention is there shown as being applied to a system for controlling and indicating the operation of a railway switch through the medium of but two line conductors 53 and 54 between the switch and its control lever. As in the case of Fig. 3, the switch to be controlled is associated with the rails 4| and 42 of a branch track which at times diverts traffic-from the main line rails l and 2-. At a point remote from the switch is a control lever 50 which is movable between two positions A and Z, respectively identified with the normal posi-- lever'5ll controls the polarity of the energywhich of these contacts is the winding of an indication" relay KQP.

Line circuit 53'54 serves the dual purpose of transmitting energy for operating the switch control relay WR and charging one or'the other The particular switch-control relay shown at WR is provided with polar contacts 55, 51 and 58 which respond tothe polarity of the energy applied to the relay winding in advance of the time that neutral contacts 59 and 60' of the relay pickup in' response to applied energy of.

either polarity When switch control lever 59 is in the uppermost or normal position designated by character A, the polarity of the energizing pulses supplied over contact X of device CT to the winding of relay WR is such as to move the polar contacts to the right position represented. When, however, the switch lever 50 is moved to the lowermost or reversed position identified with the character Z, the reversed polarity of the supplied energy causes the polar contacts of relay WR to' be shifted to the lefthand position.

In addition to the response characteristics just described, relay WR is of the delayed-release type and is designed to'hold both its polar andneutral contacts continuously in the operated position when the winding thereof receives spaced energizing pulses of the recurring-frequency character determined by the coding device CTI.

Polar contacts .51 and 58 of relay WR control the circuits of a motor (not shown) which is employed in the usual manner to operate points of the track switch with which the branch-track rails M and 42 are associated. When these contacts occupy the right position shown, the motor receives normal polarity energizing current and operates the switch to the normal position in which trafiic moving: in the direction of the arrow continues along the main line rails l and 2. When the contacts 5'! and 58 ofrelay WR occupy the left-handv position, the switchoperating motor then runs in the reverse direction and shifts the switch points into positions in which the Zraffic is diverted to-the branch-line rails and The indication relay shown at KQP also is of a polarized delayed-release type. It has a neutral contact 6| which remains continuously picked up as long as the winding of the relay receives spaced pulses of energizing current at a frequency determined by the rate of movement of the coding devicecontacts X. It also has a polar contact 62 which occupies the right position when the polarity of the winding energy is normal and the left position when the polarity of this energy, is reversed. This contact selectively completes the lighting circuits of a pair of indicating lamps A and Z which are identified with the normal and reversed positions of the referred to track switch.

Only one of the energy-storage capacitors K and KI is active at any given time,;the selection being effected by means of a pair of contacts 63 and 64 which are included in the usual switch controller and which respond to the position of the track switch points. When, as shown, these switch points occupy the normal position, contact 63 completes the circuit for capacitor K. When, however, the points occupy thereversed or trafiic-diverting position, contact 64 completes the circuit for the companion capacitor KI.

The operation of the. switch-control and indication equipment of Fig. 4 will now be explained.

When the switch-control lever 50 is in the normal position A, control-supply source Q is connected with the line conductors 53 and 54 in a manner that conductor 53 is positive with respect .to conductor 54 and the winding of relay WR. then receives periodically interrupted energizing current over a circuit which extends from the positive terminal of battery Q through conductor 66, switch blade 5|, conductor 61, front contact X of coding device CTLline conductor 53, conductor (58, the winding of switch-control relay WE, conductor 69, line conductor 54, front contact XI of device CT, conductor and switch blade 52, back to the negative terminal of battery Q. This causes the contacts of relay WR to occupy the positions represented in Fig. 4' and, in consequence, the switch-operating motor (not shown) causes the track switch points to occupy the normal positions represented in full lines.

At the same time, capacitor K receives charging current in the form of recurring pulses determined by the operation of contact X of the coding device CT! over'a circuit which extends from line conductor 53 through front contact 59 of relay WR, conductor H, switch-controller contact 63, conductor 12, the capacitor K, conductor 13, right contact 55 of relay WR, conductor 14 and front contact 65 of relay WR back to the line conductor 54.

Each time that the contacts X of the coding device CTI occupy the released position, the line conductors 53 and 54 are disconnected from. the battery supply wires 61 and 15 and connected with the winding of the indication relay KQP. During each of these periods, therefore, the capacitor K circulates discharging current through this relay winding over a circuit which may be traced from the upper or positively charged plate of the capacitor through conductor 12, switch-controller contact 63, conductor 1|, front contact 59 of relay WR, line conductor 53, back contact X of device CTI, conductor 75, the. winding of relay KQP, conductor 76, back contact XI of coding device CTI, line conductor 54, front contact 60 of relay WR, conductor 14, right contact 56 of relay WR and conductor 13 back to the lower or negatively charged plate of the capacitor.

Under the influence of these recurring pulses of normal-polarity current from the capacitor K, relay KQP maintains its contacts in the positions represented and completes for lamp A a lighting circuit which extends from. the positive terminal of a suitable supply source through front contact 6| of relay KQP, right contact 62 of the relay and the lamp A back to the negative terminal of the supply source. This lamp now lights to indicate that the track switch points associated with rails 4| and 42 occupy the normal position.

Assume now that it is desired to shift these switch points to the reversed or traffic-diverting position. Switch-control lever 50 is moved downwardly to position Z in which blades 5| and 52 reverse the connections of supply battery Q with conductors 97 and T0. The energy now supplied over coding contacts X to line conductors 53 and 54 is of a corresponding reversed polarity which causes switch-control relay WR to shift its polar contacts 56, 51 and 58 to the left-hand position. Contact 59 now includes the second capacitor Kl in the active circuit while contacts 51 and 58 cause the switch-operating motor to shift the track switch points from the normal or represented position to the reversed or trafiic-diverting position. When this shift is completed, contact 64 of the switch controller completes the before-referred to active circuit for the second capacitor KI and thus allows it to receive pulses of charging current from the line conductors 53 and 54.

Because of the reversed polarity of these pulses the lower plate of capacitor Kl is positively charged with respect to the upper plate, a relation which is reversed with respect to that of the charging of the plates of the first capacitor K. Each time that the coding-device contacts X are in the lowermost 'or released position, the winding of the indication relay KQP receives from capacitor KI this reversed polarity-charging current. In consequence, it shifts contact 62 to the left position in which indication lamp Z lights to show that the switch movement initiated by lever 50h'as been completed.

7 When it is later desired to return the switch points to the normal position, control lever 50 is moved upwardly to position A. Blades 5| and 52 now connect the supply battery Q in normalpolarity relation with the line conductors 53 and 54. Switch-control relay WR responds by returning its polar contacts to the right position in which the first capacitor K is included in the active circuit and the second capacitor Kl is disconnected. As the switch motor moves the switch points to the normal positions, switch-controller contact 63 completes the capacitor circuit just referred to and allows energy-storage device K to be periodically charged with normal-polarity energy over the coding-device contacts X. In connecting this capacitor with the winding of relay KQP during the intervals which separate the charging periods these contacts cause the winding of the mentioned indication relay again to receive normal-polarity pulses of indicating energy. In response to these pulses relay KQP completes the lighting circuit for indicating lamp A which shows that the switch movement initiated by lever 50 has been completed.

From the foregoing it will be apparent that were the coding device CTI at the switch lever location to be provided with a larger number of contacts, a correspondingly increased number of indication circuits including relays corresponding to device KQP might be operated under the control ofthe single coder.

From the preceding description of the three different applications of the code-registering means of my invention, it will be seen that in all of these use has been made of an energy-storage device K, a source of charging current Q therefor, a slow-release relay KQ which is included in a discharge circuit for the storage device, and a device provided with a contact X which periodically moves between a first and a second position respectively to complete the charging and the discharging circuit for the storage device.

In applications such as that shown in Figs. 1 and 2 this novel combination of instrumentalities provides a ready means for increasing the sensitivity of track circuit shunting. When applied in the manner of Figs. 3 and 4, it facilitates the control and indication of the operation of railway track switches.

Although I have herein shown and described only three forms of railway traffic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

'1. In combination, a section of railway track, an associated track switch, a slow-release relay for distinguishing between a vacant condition of said section with said switch in a first position and either an occupied condition of said section or a shifting of said Switch from said first to a second position, an energy-storage device connected across the rails of said section, means governed by said switch .for interrupting said device to rail connection whenever the switch is shifted out of its said first position, a source of device-charging current, and a codingcontact which repeatedly connects'said section rails first to said charging source and then to the winding of said relay whereby as long as said section remains vacant and said switch is in its said first position said rails transmit from said source to said storage device recurring pulses of currentv which charge the device and from said device to said relay winding recurring pulses of discharge current which maintain said relay continuously picked up and whereby when either .a train shunt is placed across said section rails or said switch is shifted out of its said first'position said relay is deprived of said discharge current pulses and allowed to release.

2. In combination, a section of railway track, a track switch associated with a given end of said section, a capacitor installed at said given section end and there connected across the rails of said section, means governed by said switch for interrupting said capacitor to rail connection whenever the switch is shifted from a first to a second position, a source of capacitor-charging current at the opposite end of said section, a similarly located slow-release relay for distinguishing between a vacant condition of said section with said switch in its said first positionand either an occupied condition of said section or a shifting of said switch out 'of its said first position, and a coding device which repeatedly connects said section rails first to said capacitor and then" to the winding of said relay whereby 1 as long as said section remains vacant and said switch is in its said first position saidrails transmit from said source to said capacitor recurring pulses of current which charge the capacitor and from said capacitor to said relay winding recurring pulses of discharge current which maintain said relay continuously picked up and whereby when either a train shunt is placed across said section rails or said switch is shifted out of its said first position said relay is deprived or said discharge current pulses and allowed to release.

3. In combination, an electrically controlled mechanism operable between two positions, means including a circuit for controlling said mechanism from a distant point, means also including said circuit together with a slow-releas relay at said distant point for indicating when said mechanism occupies a selected one of its positions, a source of energy, a coding contact which repeatedly connects said circuit first-to said source andthen to the winding of said indicating relay, an energystorage device, and means responsive to movements of said mechanism for connecting said storage device to said circuit when and only when the mechanism occupies its said selected position whereby the device then repeatedly receives charging current from said circuit and then also repeatedly supplies discharging current over that circuit to the winding of said indicating relay for the purpose of maintaining that relay picked up as long. as said mechanism continues in said selected position.

4. In combination, a multi-position railway switch, means including a circuit for controlling said switch from a distant point, means also including said circuit together with a, slow-release relay at said distant point for indicating when said switch occupies a selected one of its positions, a source of energy, a coding contact for repeatedly connecting said circuit first to said source and then to the winding of said indicating relay, a capacitor, and means responsive to movements of said switch for connecting said capacitor to said circuit when and only when the switch occupies its said selected position whereby the capacitor then repeatedly receives charging current from said circuit and then also repeatedly supplies discharging current over that circuit to the winding of said-indicating relay for the purpose of maintaining that relay picked up as long as the switch continues in said selected position.

5 In combination, a railway switch adapted to occupy one or another of two positions, means including a circuit for controlling said switch from a distant-point in accordance with the polarity of the energy which a direct-current source is caused to impress upon said circuit, means also including said circuit together with a polarized slow-release relay for indicating at said distant point which of said two positions said switch occupies, a coding contact for repeatedly connecting said circuit first to said source and then to the winding of said indicating relay, a pair of capacitors, a polarized switch-control relay arranged to connect one or the other of said capacitorsto said circuit in accordance with the polarity of the coded. energy which is received therefrom, and means responsive to the movement of said switch to its position of polarity determined control for connecting the actively selected capacitor to said circuit in a manner that it receives charging current therefrom and supplies discharging current thereover to'the winding of said indicating relay,

6. In combination, an electrically controlled mechanism operable between two positions, a

manually operable lever for determining the position of said mechanism, a combined control and indication'circuit which extends from said lever to-said mechanism, a source of control energy and a polarizedindicating relay at the location of said lever, similarly located coding means which repeatedly connect said circuit first to said source and then to the winding of said indicating relay, means governed by said lever for selecting the polarity of the time-spaced pulses of control energy which said circuit receives from said source through said coding means, a polarized mechanism-control relay connected with said circuit at the location of said mechanism and functioning to determine the position of the mechanism in accordance with the polarity of the said control energy pulses which said circuit transmit to the relay, a pair of enorgy-storage devices also at said mechanism location, means governed by said control relay and also responsive to the polarity of said received control energy pulses for setting up a connection of one or the other of said devices with said circuit, and means responsive to the movement of said mechanism to its position of desired control for completing the thus set up storage-device connection and thereby causing the therein included device to receive from said circuit pulses of charging current which recur in step with and have the same polarity as said time-spaced pulses of control energy and to supply to that circuit intervening pulses of discharge current which fiow over the circuit and through said coding means to the winding of said polarized indicating relay.

7. In a system for controlling a two-position railway switch from a distant point and for indicating th position of said switch at that distant point, a combined control and indication circuit comprising a pair of conductors whch extend from said point to said switch, a source of control energy and a polarized slow-release indicating relay at said point, similarly located coding means for repeatedly connecting said circuit conductors first to said source and then to the winding of said indicating relay, switch position changing means also at said point for selecting the polarity of the time-spaced pulses of control energy which said conductors receive from said sourc through said coding means, a polarized switch control relay connected with said circuit conductors at the location of said switch and functioning to determine the position of the switch in accordance with the polarity of the said pulses of control energy which the relay receives from said conductors, a pair of energystorage devices also at said switch location, means governed by said control relay and also responsive to the polarity of said received pulses of control energy for setting up a connection of one or the other of said devices with said circuit conductors, and means responsive to the movement of said switch to its position of desired control for completing the thus set up storage-device connection and thereby causing the therein included device to receive from said conductors pulses of charging current which recur in step with and have the same polarity as the said timespaced pulses of control energy and to supply to those conductors intervening pulses of discharge current which flow over the conductors and through said coding means to the winding of said polarized indicating relay and cause that relay to show the position of said switch.

8. In combination, a mechanism which may occupy one or another of a plurality of difierent positions, an indicating relay installed at a point remote from said mechanism, an energy-storage device at the location of said mechanism, a circuit which extends between said remote point and said mechanism and over which energy may be transmitted both to and from said device, means responsive to movements of said mechanism for connecting said device to said circuit when and only when the mechanism occupies a selected one of its said positions, a source of charging current for said device located at said remote point, and a coding contact also at said remote point which repeatedly connects said circuit first to said charging source and then to the winding of said indicating relay whereby when and only when said mechanism is in its said selected position said circuit transmits from said source to said storage device recurring pulses of current which charge the device and from said device to said relay winding recurring pulses of discharge current which energize said relay.

9,. In combination, a railway switch which may occupy one or another of a plurality of different positions, a position-indicating relay of the slow-release type installed at a point remote from said switch, a capacitor at the location of said switch, a circuit which extends between said remote point and said switch and over which energy may be transmitted both to and from said capacitor, means responsive to movements of said switch for connecting said capacitor to said circuit when and only when the switch occupies a selected one of its said positions, a source of charging current for said capacitor located at said remote point, and a coding contact also at said remote point which repeatedly connects said circuit first to said charging source and then to the winding of said indicating relay whereby when and only when said switch is in its said selected position said circuit transmits from said source to said capacitor recurring pulses of current which charge the capacitor and from said capacitor to said relay winding re curring pulses of discharge current which hold said relay continuously picked up. v

10. In combination, a section of railway track, a track switch associated with said section, a relay for distinguishing between a vacant condition of said section with said switch in a first position and either an occupied condition of said section or a shifting of said switch from said first to a second position, an energy-storage device connected across the rails of said section, means governed by said switch for interrupting said device to rail connection whenever said switch is shifted out of its said first position, a source of charging current for said device, and a coding contact which repeatedly connects said section rails first to said charging source and then to the winding of said relay whereby as long as said section remains vacant and said switch is in its said first position said rails transmit from said source to said storage device recurring pulses of current which charge the device and from said device to said relay winding recurring pulses of discharge current which energize said relay and whereby when either a train shunt is placed across said section rails or said switch is shifted out of its said first position said relay is deprived of said energizing pulses of discharge current.

11. In combination with a section of railway track, shunting-sensitivity increasing means therefor comprising an energy-storage device bridged across the rails of said section at one end thereof, a source of device-charging current at the other end of the section, a relay for distinguishing between vacant and occupied conditions of said section, and a coding contact which repeatedly connects said section rails first to said charging source and then to the winding of said distinguishing relay whereby as long as said section remains vacant said rails transmit :from said source to said storage device recurring pulses of current which charge the device and from said device to said relay winding recurring pulses of discharge current which energize that winding and whereby when a train shunt is placed across said section rails there is an initial flow to that shunt of current from said storage device as well as from said charging source.

FRANK H. NICHOLSON. 

